Container base



FIG. 1 is a perspective view showing our new design;

FIG. 2 is a front elevational view, the rear elevational view being a mirror image thereof;

FIG. 3 is top plan view; and,

FIG. 4 is a bottom plan view.

Any broken lines in the drawings depict probable environment only and form no part of the claimed design. 

The ornamental design for a “container base”, as shown and described. 